It is my pleasure to welcome you to this conference on High Speed Photography, Video-graphy, and Photonics just one year almost to the day since we welcomed a large audience of delegates and attendees to the 15th International Congress on High Speed Photography and Photonics. The size and scope of that meeting clearly indicated the continuing importance and strength of this field. It is, perhaps, a more exciting and growing field today than at any time in the past. What other field can claim to cover fifteen to twenty orders of magnitude as all in a day's work?: Certainly those of you here are doing just that as you use the technology to record slowly changing events and play them back at much higher speeds to study the changes in the phenomena being observed and also to investigate the phenomena and events in the picosecond and even femtosecond regimes.

The variety, range and precision of methods available for photographic recording of fast phenomena have been increasing steadily. The capabilities of some of the newer techniques will be described. At the lower end of the speed range, the advances have been mainly in improvements in resolution, and in the introduction of video techniques. At the highest speeds the advances have included increases in dynamic range, a wider acceptance of image tubes, and a more careful analysis and characterization of their limitations. The variety, range and precision of methods available for photographic recording of fast phenomena have been increasing steadily. The capabilities of the newer techniques are considered, classifying the methods by the kind of record obtained. Descriptions of experimental techniques and apparatus, and illustrations, are given in an earlier article entitled, "A Review of the Methods of High-Speed Photography," published in Reports on Progress in Physics in 1957;[1 and in "Advances in High Speed Photography 1957-1972" published in the Proceedings of the Tenth Internatiopal Cngress on High Speed Photography (HSP10) [116 and also in JSMPTE 82 167-175 (1973). L117o This present paper is in the nature of a survey of the limits to which the various techniques have been pressed as compared to the limits attained, or reported in the open literature, at the date of the reviews 10 and 25 years ago. There are a number of recent books and articles which also provide excellent surveys and impressive bibliographies:129 -138 Streak records with drum cameras can give a time resolution of 5 x 10-9 s.[2,3] Rotating mirror streak cameras with a single reflection[15] at present approach 10-9 s and may with multiple reflections achieve 10-10 s. The Schardin limit[ 4] for presently available rotor materials is 0.25 x 10-9 s, but this is predicated upon a single reflection of the light beam from the rotor and can be surpassed if the camera is designed to take advantage of multiple reflections. Deflecting image converters go much further: 5 x 10-13 s [5-12,115,125,139-13] (see Table I). There has been a notable increase in the last ten years in the use of image converter tube cameras of many kinds particularly for the study of laser pulse structure and for investigations of electrical breakdown. Deflecting image converter tube cameras are now also being used for studies at UV and shorter wavelenghts - though the time resolution is somewhat longer than for visible light studies.[123] Twenty-five percent of all papers presented at recent HSP Congresses involve ICTs. Single flashes of light, bright enough for silhouette recording, can be as short as 3 x 10-14 s[118,137,138I and similarly short for reflected-light recording for small near objects, or 10-12 s for a field of view a meter square or more. The very short flashes just mentioned are laser flashes. The availability in many labs of picosecond laser pulses is one of the significant advances of the decade. The power in the laser flash can be very high, but it should be noted that the integrated energy in the flash is always less than the energy in the flashlamps or primary lasers that pump the laser. There has been a steady advance in the design of open sparks and of gas discharge tubes and associated equipment, though this light output is rarely briefer than N/107 where N is the stored energy in joules. [16-26,129-131] Electrically driven Kerr cells can operate with an exposurc of 5 x 10-10 s. Optically driven Kerr cells can give exposures of a few picoseconds.[32) Simple image converter tubes can work at 10-10 s and with greater light transmission than Kerr cells.[7,30,311

The 15th International Congress on High Speed Photography and Photonics was a gathering of international representatives who presented papers on the latest developnents on the use of high speed photography for scientific, industrial, research, medical and educational purposes.

Flash x-ray diagnostics of high speed dynamic tests need to be reliable as the test may be quite expensive and time consuming. Preparation for a first time test can involve many partial or preliminary tests to verify adequacy of x-ray energy, x-ray exposure, film/screen combination, film holder protection, flash x-ray generator protection, triggering and timing techniques. Once these preparations have been successfully completed, very informative results are attainable for a variety of tests including jetting, welding and casting.

The Neurosurgeon faces a dilemma, that is, how to treat and reconstruct the injured skull and brain with limited knowledge as to how the injury occurred. In an attempt to understand such injuries, our group assembled a series of acceleration sleds to experimentally reproduce these injuries in primates and high frame rate flash x-ray cine system to radiographically study their time course.

Demountable photocathode X-ray streak camera developed for X-ray diagnostics in ICLF experiments is described. The system can be installed to the experimental chamber via gate valve furnished at one end of the front end chamber, the other end of which is connected to the streak tube. Remarkable features of the system are demountable photocathode scheme which enables to change the photocathode very easily and quickly, demountable accelerating mesh electrode, gate valve which enables the system to operate independently from the experimental chamber, differential pumping scheme which keeps the_vacuum_in the streak tube better than 10 6 torr while the front end is evacuated down to 10 ~ 4 % 10 05 torr through the gate valve and data taking scheme such as a film back or SIT TV camera combined with a temporalanalyzer. Typical performances of the system are characterized by the sensitivity of the photocathode to the soft X;ray ranging from 100 eV to 10 keV because of a 300 Å Au photocathode deposited on a 1000 Å Parylene film, the streak sweep rate of 1 ns/15 mm to 10 ns/15 mm, the streak trigger delay time of 20 ns to 30 ns and the excellent low trigger jitter less than ±20 ps. Simultaneous gating of the photocathode of the streak tube and the MCP in image intensifier gives low back ground output image. Preliminary test of the system showed that the system has a temporal resolution of 17 ps and a limiting dynamic spatial resolution of 20 1p/mm along the 10 mm useful photocathode slit at the fastest sweep rate of 1 ns/15 mm.

The Directed Energy Group at BDM Albuauercrue, in cooperation with and for the Directed Energy Directorate of the U.S. Army, MICOM, Redstone Arsenal, Huntsville, Alabama, has deve-loped a concept to achieve an effective ten million frames-per-second infrared videography for intensity distribution diagnostics of high power CO₂ laser pulses. The concept uses separate pyroelectric surfaces, either vidicons or self-scanning arrays, for each desired frame of data. The pyroelectric surface acts as analog storage of the image until such time as it can be digitized and read into data storage between laser pulses. Each pyroelectric surface is shuttered in sequence by Pockels cells, with adjust-able shutter "on" times and frame-to-frame timing as short as 100 nanoseconds.

The curved-channel microchannel plate (C² MCP^TM) is the latest development in high gain microchannel technology. This new electron multiplier demonstrates many significant improvements over standard microchannel plates. Standard MCPs suffer from limited gain and ion feedback. The ion feedback is produced when residual gas molecules within the channels are ionized by secondary electrons. These positively charged ions now travel back through the channel, acquiring sufficient momentum to produce secondary electrons when the ion strikes the channel wall. These secondary electrons are in turn multiplied and result in spurious output pulses. In other instances the ion may leave the channel entirely and, in the case of image tubes, impinge upon the photocathode causing ion poisoning which eventually degrades the quantum efficiency of the cathode. In order to operate a microchannel plate in the high gain analog mode or photon counting mode, it becomes necessary to limit ion feedback. In the C2 MCP this is accomplished by curving the channels to a sufficient radius to reduce the distance an ion can travel prior to striking the channel wall, thus restricting its momentum and probability of producing secondaries which cause spurious pulses, which in turn degrade the noise figure. By substantially reducing the rate of ion feedback, it now becomes possible to operate a single MCP at gains in excess of 106, and since the C' MCP is a single piece electron multiplier, the spatial resolution of the electron image is maintained. The C² MCP offers low noise uniform gain with either analog or pulse saturation outputs. The C² MCP can be custom fabricated per customer dimensions.

The Long Life Microchannel Plate is a new version of the microchannel plate. The glass structure is specially formulated for high temperature processing. It offers superior electrical characteristics. Its features are: 1. Longevity - substantially greater electrical stability of the strip current and gain. 2. Superior dark noise to that of the standard microchannel plate. 3. Can be recycled more than the standard microchannel plate. 4. Can be vacuum baked at higher temperatures for optimum tube outgassing and better performance. In-house MCP electrical life test has shown that in three separate experimental cycles, Long Life Microchannel Plates are substantially more stable than our standard microchannel plates. The U. S. Army's Night Vision Laboratories have evaluated two tubes with L2 MCPs. The results were: superior MCP electron gain, better strip current and dark noise than a tube which was built with a standard microchannel plate.

Soft x-ray streak cameras are used in conjunction with several instruments for the diagnostic of laser irradiated targets. A program was undertaken to develop cameras satisfying the requirements of the laser facility, to improve the reliability and performance of the camera and to reduce the level of effort required to set and operate each diagnostic. The implemented soft x-ray streak cameras can be operated either manually or automatically.

Optical shutters with exposure times approaching 1 ns have been achieved by gating either the photocathode or the microchannel plate of 18-mm proximity-focused microchannel plate intensifier tubes. We present measurements of the shutter performance, including the total optical gate, uniformity vs time, resolution, linearity, and dynamic range, for a number of intensifier tubes under various types of pulsing configurations. Properties of intensifier tubes related to fast gating and limitations on the gating speed imposed by the intensifier tube geometry are discussed. We also give results with a specially modified intensifier in which all but a 3 mm x 18 mm portion of the photocathode was masked off by an opaque metallic undercoating, along with preliminary results of gating third-generation (GaAs photocathode) intensifier tubes. A characterization procedure used to evaluate the performance of each optical shutter is discussed, along with a review of fast electrical pulsers suitable for gating intensifier tubes.

A gated x-ray intensifier is described for use in laser produced plasma experiments. Results show that the temporal resolution is ≈ 50 ps. Factors affecting the design are discussed.

We have built an x-ray streaked crystal spectrograph for making time-resolved x-ray spectral measurements. This instrument can access Bragg angles from 110 to 38° and x-ray spectra from 200 eV to greater than 10 keV. We have demonstrated resolving powers, E/▵E > 200 at 1 keV and time resolution less than 20 psec. A description of the instrument and an example of the data is given. We have combined a Bragg diffraction crystal with an x-ray streak camera in order to time resolve the x-ray spectra from laser-produced plasmas. The resolution is sufficient to resolve individual lines in the x-ray spectra and measure their time history. These x-ray spectral measurements can be an important plasma diag nostic. Relative intensities of various x-ray lines can be used to infer plasma temperatures and densities.1 Also, if there is sufficient energy resolution, stark-broadened individual line profiles are a plasma density diagnostic.2 The streaked spectrograph can also assist in developing a short-pulsed x-ray line source. Such a short-pulsed x-ray line source is needed for making time-resolved short-pulsed absorption measurements, such as those proposed for measuring the core size of an ICE pellet.3 The instrument discussed here has been developed at LLNL for use on our Novette laser system. It uses an elliptical curved crystal focusing design to concentrate the x-ray spectrum onto the streak camera s1it.4 With such a design we have obtained moderately high resolving powers of E/▵E > 200 at x-ray energies around 1 keV. The instrume,lt is versatile, being able to cover spectral regions from 200 eV to 10 keV. This is accomplished by usin9 various geometries which change the Bragg angle in the range from 110 to 38° and by using various dificacting crystals. For the first application, whose results we present here, we have measured spectra in the 1 keV range using a KAP crystal (2d=26.632Å). The final and most important feature of the instrument is that it uses an existing LLNL streak camera with little modification. The spectrograph design takes advantage of the point-to-point focusing properties of an ellipse. X rays emitted from the laser-produced plasma placed at one of the foci of the ellipse will be reflected from the elliptical surface converging on the other focus of the ellipse. This is shown schematically in Fig. 1. A Bragg diffraction crystal is elastically bent to conform to the elliptical surface. Each ray is reflected from the surface at their unique Bragg angle, providing wavelength selection. The streak camera is then placed in the far field behind the focal spot and measures the dispersed spectrum. The dispersion of the system depends on the geometry of the ellipse and the distancP of the streak camera slit from the focal spot.

We have made time-resolved spectral measurements above 80 Å from laser-produced plasmas. These are made using a transmission grating spectrograph whose primary components are a cylindrically-curved x-ray mirror for light collection, a transmission grating for spectral dispersion, and an x-ray streak camera for temporal resolution. A description of the instrument and an example of the data are given. We have built a spectrograph to time resolve the spectrum above 80 A from laser-produced plasmas. Several possible schemes using high-powered lasers have been identified that produce x-ray lasing lines in the 80 Å to 300 Å range.1 This spectrograph has been built to measure the output from these targets. The principal components of the spectrograph are a cylindrically-curved x-ray mirror for light collection, a transmission grating for wavelength dispersion, and a soft x-ray streak camera for x ray detection. These have been combined to produce an instrument having high spectral resolution, E/tL > 200, continuous wavelength coverage from 80 A to 300 A, good time resolution, 1,20 psec, and high sensitivity, 1,10 photons/sec-sr. In addition, because an application is to measure x-ray lasing output, we have devised an optical alignment system which can accurately point the instrument to the target with an accuracy of less than one milliradian. A schematic of the instrument design is shown in Fig. 1. X rays from the target are collected and focused at the detection plane by a cylindrically-curved grazing incidence x-ray mirror. The mirror acts like one element of a Kirkpatrick-Baez x-ray microscope producing a line focus perpendicular to the plane of dispersion. 2 The mirror has an eight meter radius of curvature and operates at an angle of incidence of 4°. It is 68 cm from the target midway between the target and detection circle. This produces a magnification of unity. Spherical aberrations for these conditions are estimated to be less than 10 μm, which is much less than target sizes.

The direct drive approach to laser fusion, in which laser produced ablation of the surface of a spherical shell target induces a high compression of the enclosed fusion fuel, requires a high degree of irradiation uniformity. Diagnosis of the trajectory of this imploding shell can, in principle, provide valuable information on the uniformity of the implosion, as well as verify the predictions of hydrodynamic code simulations. This requires time-resolved x-ray photography of the imploding shell with high temporal (~ 10 ps) and spatial (< 10 μm) resolution. We report recent time-resolved x-ray photographic measurements of the implosion of large aspect ratio (- 200) glass microballoons driven by symmetric nanosecond 1.05 pm radiation at moderate intensities (~ 1014 W cm^-2) from the 24-beam OMEGA laser facility. Time-resolved x-ray photography was provided by a pinhole camera system having a magnification of - 13, coupled with a specially designed x-ray streak camera. The latter included a gold photocathode deposited on a Be substrate, had an electrooptic image magnification of ~2.2, and was of an all re-entrant design. The use of a fine scale accelerating mesh and an extraction field of ~ 10 kV cm 1 produced a spatial resolution 20 1pm across the 8 mm slit photocathode. Temporal resolution of the instrument with the present ~2 ns streak duration was ~ 20 ps. Since the imaging and electrooptic system was in close proximity to the hostile environment of the target with-in the target chamber, special precautions were required to preserve the integrity of the electrooptic system.

Uses for high speed videography have become increasingly diversified and, in some cases, more sophisticated. In order to meet the needs of a growing number of high speed video users, new advances in technology have been developed which serve to extend the capabilities of the basic system. This paper discusses the new accessories to the Spin Physics SP2000 Motion Analysis System as well as a number of case histories illustrating their uses.

The integration of new technologies such as video and auto focus devices with existing high-speed photographic instrumentation is considered. For a great percentage of daytime activity the desert atmosphere is shown to be a limiting factor for collection of visual data. Atmospheric considerations are shown to be an important consideration for future instrument design.

Great difficulty is typically encountered in evaluating the performance of recorders, particularly during playback, for use in high-speed videography systems. A field-sequential unique pattern is described which may be implemented with digital circuitry, and which quickly and without ambiguity permits this evaluation. The pattern generator also is useful as a "pseudo camera" in development work on videography systems over a range of frame rates.

The Spin Physics SP-2000 high-speed video system can be combined with an x-ray source, a dynamic event having internal (not directly visible) movement and an x-ray image intensifier to perform dynamic radiography. The cesium iodide input fluor and P-20 output fluor of the image intensifier have rapid decay to allow x-ray imaging up to 12,000 pictures per second. Applications of this technique include internal functioning of a compressor, turbulent water action and other mechanical actions.

In the early days of shock wave investigations of the dynamic high-pressure properties of solid materials, the shock wave diagnostics consisted primarily of measurements of the shock velocity and the peak particle velocity in the shocked specimen. By the decade of the 1960's, however, it was already well recognized that the measurement of time-resolved particle velocity history or stress history, as opposed to only peak values, could provide valuable additional information concerning such material properties as phase changes, yield strengths, and rate effects.1

The Fabry-Perot laser velocimeter is used at LLNL for hydrodynamic, equation-of-state, surface-ejecta mass measurements and for other applications. Velocities of shocked surfaces can be measured to better than 1%, and multiple records can be superimposed on a single piece of film. Many phenomena are being investigated for possible sources of error. One concern was whether the direction of the surface normal could affect the measured Doppler shift, or whether the direction of the particle velocity was sufficient to determine the shift. A series of experiments with angles between the laser and particle velocity as small as 20° have shown that for the surface smoothnesses that we encounter, we see no effect caused by varying the direction of the surface normal.

An optical technique is described which uses velocity interferometry to determine the particle velocity changes associated with plane shear wave propagation. In this technique, two velocity interferometers are used to monitor different diffracted laser beams from a surface which undergoes both longitudinal and shear motion. Fringes produced in the interferometer are proportional to a linear combination of both the longitudinal and shear components of the free surface velocity. By obtaining two independent recordings of the motion, the two velocity components can be determined. Selected examples of shear wave interferometry applications are reported.

VISAR performance can be improved while reducing cost, set up time, and required operator skill. Simple features that increase laser light efficiency, improve signal-to-noise ratio, reduce the number of data channels, greatly simplify data reduction, ease VISAR adjustments, and reduce laser wear and tear are discussed. These features were collected, developed, tried, and proven over the last few years and several hundred VISAR shots.

VISAR instrumentation has been used to examine how compressive waves grow towards detonation in granular explosives. In the experiments, a variety of initial waveforms have been generated in explosive samples using planar impact techniques and carefully designed projectile and target assemblies. Despite limitations due to window interfaces, VISAR measurements have provided important insights into initiation processes, and have contributed to a useful data base for the evaluation of predictive models.

A laser interferometer is used in experiments which probe the thermal initiation and burning of explosives on a microsecond time scale prior to detonation. In this work, small charges of HMX are confined by a piston in a steel chamber bore and thermally initiated with a foil on one surface of the chamber which is suddenly heated by a capacitor discharge. The burn process is observed through the motion of a piston which is driven by the gaseous combustion products. An air-delay leg VISAR velocity interferometer system is used to monitor the piston motion. This velocity data is directly processed to determine the chamber gas pressure as a function of volume during the piston expansion. High-pressure burn rates during deflagration can be deduced from these tests. Parasitic effects in small charge experiments due to thermal conduction from the walls, piston leakage, friction, as well as the interferometer resolution itself are discussed.

In the past, ruby lasers with pulse energies of joules have been used to perform holographic interferometry on fast-changing objects. The very short (20 to 40 nanosecond) pulse of the ruby laser was used to freeze the motion of the object in time to permit holographic recording of the object. However, the ruby laser is limited to only two to three pulses at a high strobe rate. By acousto-optically strobing an argon laser, a real-time holographic interferogram can be viewed and the fringes recorded at rates of DC to 10 kHz. The pulse length of the strobed argon laser is limited by the required amount of energy. Pulse lengths of a few microseconds only provide micro joules of argon laser light Therefore strobed argon is not practical for recording holograms of dynamic diffuse object The metal vapor laser has been found to be a reasonable compromise between ruby and strobe, argon. Continuous repetition rates of a few Hz to over 10 kHz have been shown with pulse lengths comparable to that of a ruby laser and with pulse energies that are orders of magn tude higher than an argon laser. This paper discusses the measured parameters and limitations of each of these laser sources. The specific results presented were obtained with each laser in the study of structural dynamics. Future applications of the metal vapor laser are also discussed.

Measuring particle velocities in the Fourier transform plane of double and multiple exposure holograms is discussed. Both in-line far-field and off-axis holograms are considered. If the functional form of the velocity distribution curve is known then the mean and standard deviation can, in some cases, be measured directly from the transform pattern. This procedure is illustrated for a gaussian distribution. Also, a hybrid system for measuring two-dimensional particle velocities is proposed which does not require prior knowledge of the input distribution curve. The system involves sampling the transform plane intensity distribution with a TV camera, digitizing this information and finally, computing the particle velocities. Computer simulations and an actual system output are presented.

Pulse generation from 04 Laser beams is of a particular interest on the study of fast or arbitrarily moving objects as in biology and medicine. A hybrid system has been developed to generate a set configuration of pulses with: i) control over the number of pulses; ii) presetting of the individual pulse width and pulse separation; iii) synchronization of the pulse set (either interlaced TV synchronism or other external signal). The control and shaping of the pulses is based on a microprocessor that drives a modulator of high extinction ratio. The system allows the implementation of the twin pulse illumination technique previously described with particular interest to the observation of anisotropy in phase velocity propagation. This has been applied to the examine of bone heterogenety both in macerate and fresh bone and fracture mechanism. It is also belived that wearing, delamination, crack detection,and fluid or heat transport phenomena can be studied. The design of the system was inicially mainly intended for E.S.P.I. but certain advantages have been found in its use in holography. Versatility of the system was introduced in view of exploring other features and applications. This includes other pulse combinations, in particular, triple pulse, and time lapse TV target scanning suppression for slow motion objects and low light levels. Details of the system conception hardware and prospects on the system application in E.S.P.I. and Holography will be discussed with consideration of the main advantages and limitations.

A Fabry-Perot velocity interferometer system is described that uses a modified rotating-mirror streak camera to record the dynamic fringe positions. A Los Alamos Model 72B rotating-mirror streak camera, equipped with a beryllium mirror, was modified to include a high aperture (f/2.5) relay lens and a 40-mm image-intensifier tube such that the image normally formed at the film plane of the streak camera is projected onto the intensifier tube. Fringe records for thin (0.13 mm) flyers driven by a small bridgewire detonator obtained with a Model C1155-01 Hamamatsu and Model 790 Imacon electronic streak cameras are compared with those obtained with the image-intensified rotating-mirror streak camera (I2RMC). Resolution comparisons indicate that the I2RMC gives better time resolution than either the Hamamatsu or the Imacon for total writing times of a few microseconds or longer.

This paper discusses experiments in which 2 to 200-pm-thick aluminum foils were irradiated with Nd/YAG laser pulses at 3-4 GW/cm2 for 10 nsec. An optically recording velocity interferometer system (ORVIS) was used to record the resulting particle-velocity histories with nanosecond resolution. Results show that foils suspended in air are accelerated, over a period about three times the length of the laser pulse, to a final velocity inversely proportional to foil thickness. A 12-pm-thick foil attains a peak velocity of 0.2 km/sec. Foils confined by water undergo most of their acceleration during the laser pulse and attain surface velocities three times greater than do air-suspended foils of the same thickness.

Starting with a pair of signals obtained by electronically subtracting photodetector outputs from any VISAR, it is possible to plot velocity vs time, velocity vs distance, and distance vs time in 21/2 min using an LSI-11/23 computer. This includes time for six iterations of time shift with the resulting polar plots and operator interactions. The velocity calculating algorithm and a flow chart of the computer program are presented.

Application of laser interferometry to measurements of projectile motion in guns has led to resolutions of < 5pm in displacement, < 0.01 m/s in velocity, and < 0.1 μsec in time. These resolutions far exceed those available from alternative techniques such as microwaves, optical light beams, accelerometers, high-speed photography, etc., and promise to give designers of projectiles and guns a more accurate tool with which to substantiate their calculations and to optimize their designs. This paper describes two types of interferometers and their application to the measure-ment of motion of projectiles launched by conventional weapons and by smooth bore laboratory guns. A displacement interferometer, developed at RARDE, was used to measure the effects of engraving of the projectile driving band on overall projectile motion. From these measurements, the time-dependent frictional forces arising from the engraving process were calculated, providing information both on the engraving process and on the interpreta-tion of the pressure-time measurements made in the gun chamber. Measurements made with the velocity interferometer, first developed at Sandia National Laboratories, Albuquerque, ex-amined both initial motion and total travel of projectiles in smooth-bore gas guns over a velocity range of < 40 m/s to > 4000 m/s, demonstrating the wide dynamic range of the in-strument. Initial applications of this interferometer were to check the accuracy of hydrocodes used to predict the performance of two-stage light gas guns. The paper describes the design of the interferometer systems, their capabilities and limitations, and summarizes several of the uses to which they may be put as high-resolution diagnostics for measurement of gun parameters.

We describe the present capabilities of a Perot Fabry velocimeter used in the study of shock waves. The main characteristics of this velocimeter are : the ability to give two measurements in the same experiment, a duration of the record in the range 500 ns - 200 μs, an accuracy of - 2 m/s, the possibility of velocity measurements of specular reflecting surfaces or scratched surfaces, the velocities being measured in the direction of the normally reflected beam or in a direction making some angle from the normally reflected beam. The application of this velocimeter to the study of polystyrene submitted to a shock loading followed by unloading is shown. The shock polar is described by three segments in which the relation between shock U and material velocities u are U = 2,6 + 1,46 u if u< 2,82 km/s ; U = 2,03 + 1,41 u if u > 3,6 km/s and U = 5,23 + 0,52 u in the intermediate range.

An experimental requirement to generate shock waves in noble gases from detonating explosive charges and to minimize the usual disruptive effects associated with these charges led to the development and evaluation of an imploding shock wave system based on the use of nitroguanidine, which is a low-density explosive. The explosive surrounded an aluminum tube, the inside of which was filled with argon. The nitroguanidine was initiated at its periphery in such a manner that a cylindrically imploding detonation sent an imploding shock wave through the aluminum tube and into the argon gas. The experimental evaluation of this system was conducted by means of high speed photographic instrumentation, to verify that the imploding detonation in the nitroguanidine was symmetrical, and to observe the reflection of the imploding s!)ock wave in argon at the axis of symmetry. The resulting streak camera records clearly revealed the times at which the shock wave entered the argon gas and at which the shock wave reflected from itself at the center of implosion. The observed shock velocity in the argon was in good agreement with the theoretical value calculated from the shock Hugoniot compression curves for the various materials utilized in the experiment.

A photographic system is described which records the near surface combustion of a solid rocket propellant burning in an acceleration field. Strands of propellant which contain aluminum powder were photographed while burning in a pressure vessel (bomb) which is mounted on a centrifuge table. A lens and series of mirrors magnify and relay the image from the spinning bomb to a rotating prism camera. The trajectories of burning aluminum particles (50-1000μ in diameter) were investigated at framing rates of 4000 pps and unity magnification. A description of the centrifuge and photographic system is presented along with representative results derived from the film analysis.

This paper is concerned with the use of a Beckman & Whitley Model 189 framing camera to observe the initiation of detonation in cylindrical explosive charges by the detonation of a concentric outside layer of sheet explosive initiated at one end. Experiments were con-ducted with nitromethane, which is a transparent liquid explosive, and aluminum-potassium perchlorate, which is a binary mixture of fuel and oxidizer powders. The use of the transparent explosive permitted viewing along the entire length of the charge axis, so that the time of the nitromethane initiation as a function of the position of the concentric sheet explosive detonation could be observed. In the case of the binary charge, the experiment involved the simultaneous viewing of both the side and the end of the charge by a judicious positioning of two front-surface mirrors. One of these was oriented at the end of the charge at an angle of 45° with respect to the charge axis. The second mirror, larger in size, viewed the entire system, and was destructed at 656 psec by an explosive backing charge to preclude the possibility of film rewrite. Framing rates for both experiments were approximately 250,000 frames/sec. The induction time to initiation of detonation in the nitromethane was measured to be about 20 psec. However, the induction time for the aluminum-potassium perchlorate charge was too long to be recorded by the Beckman and Whitley camera. For this and other pyrotechnic dharges, it was necessary to use a slower writing Fastax camera recording at a rate of 2000 frames/sec; the induction times for the pyrotechnic systems were in the neighborhood of 1 to 3 msec, which is two orders of magnitude longer than for the nitromethane.

Recent advances in high time-resolution optical diagnostic instrumentation for shock wave experiments in condensed media (especially time-resolved spectroscopy) have resulted in new challenges concerning the timing of such experiments. We present a technique for detecting the passage of a shock wave by the generation of an optical Fiducial signal, which can be detected and recorded directly by the optical recording device (typically a streak camera). This technique, which is based on Stress-Induced Defeat of Total Internal Reflection (SIDTIR), requires only simple apparatus and set up, and offers fiducial transition times as short as 50 psec in a reasonable experimental configuration.

The body of a pedestrian, who is impacted by a vehicle, often executes a complicated spatial motion during the collision. In experimental impacts under laboratory conditions high-speed cinetechniques lend themselves to be utilized for analysing the characteristics of such spatial motions providing that at least two time-matched views of the scene are available. In order to facilitate an efficient analysis of the motion phenomena associated with simulated vehicle-pedestrian collisions, a computercontrolled film scanning system was developed which is based on a stop-frame film transport, a video-dissector, and a video-speed image RAM. The random-access features of the dissector enable a fast automatic film frame analysis while the high speed of the image memory allows to constantly observe the scanning procedure, if necessary. Marker identification is performed under operator control utilizing the interactive features of the system. An assessment of the accuracy of the automated reconstruction of spatial marker trajectories revealed that moving objects are in general located to an accuracy of better than 7mm in a scene of typically 7m in diameter. The application of the method to experimental vehicle-pedestrian impacts is demonstrated.

The vibration error of high. speed camera can be measured in real time by laser and position sensing detecting system. This system enable non-contact highly sensitive measurement. It consists of a He-Ne laser position sensing detector and electronic circuits. The floor vibration and the total vibration are measured. Further improvement for real time feedback a damping force to balance the vibration are suggested.

Small ( 2 mm ) diameter plastic flyer plates are used to impart known pressure-time pressure pulses in test samples. The plates are launched at velocities from 0.2 to 2.0 mm/μ seconds and remain planar during flight and impact. During plate impact the velocity of each plate is determined by streak photography.